JPS6328009Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a hydraulic system for running a vehicle equipped with a hydraulic motor that enters a freewheeling state when the supply circuit pressure of the hydraulic motor is below atmospheric pressure. It is.

[Conventional technology]

It can run freely on rough terrain, and if the wheels get stuck in a dent or flexible spot on rough terrain, it can be easily escaped (hereinafter referred to as derailment).
Furthermore, examples of vehicles that can climb steep hills include jeeps that use a four-wheel drive system. This four-wheel drive system connects an auxiliary transmission to a gear transmission, and its output shafts are both front and rear, each consisting of a universal joint, propeller shaft, and differential reduction gear. A fairly complex power transmission system is connected to drive the front and rear wheels simultaneously.

[The problem that the idea aims to solve]

By the way, 4-wheel drive vehicles do not require the same high-speed driving as a Jeep, and only need to be able to travel on the road at a maximum speed of about 15km/h, such as agricultural transport vehicles or special vehicles for civil engineering construction. , which has not been used in the past because it causes a significant increase in cost. However, it goes without saying that there is a need for a vehicle that can run freely on rough terrain even if the running speed is not high, that can easily derail itself, and that has excellent hill climbing ability.

This idea is useful for vehicles that require driving on rough terrain,
For example, in an agricultural transport vehicle, it is not necessary to be able to use four-wheel drive at any speed, as with a jeep, but it is possible to use four-wheel drive in first gear, that is, at a low speed. ,
The technical challenge was to greatly improve performance on rough terrain, off-wheel operation, and hill climbing ability compared to conventional two-wheel drive vehicles of this type. be.

[Means to solve the problem]

As a means for achieving the above-mentioned object, this invention configures a vehicle running hydraulic system as follows. That is, the vehicle running hydraulic system according to this invention is rotatably supported on an eccentric shaft of a fixed main shaft of a front wheel of a vehicle having an engine-driven rear wheel, and a plurality of cylinders are disposed on the axis of the eccentric shaft. a cylinder block equally spaced radially toward the piston; a piston fitted in each of the cylinders of the cylinder block and having a through hole for introducing pressure oil in the center and a pocket on the top end surface; the top end of each of these pistons; A casing that has a piston pressing surface that is in close contact with the peripheral edge of the surface, is rotatably supported by the fixed main shaft and forms a front wheel hub part, and a casing that passes through the fixed main shaft and has two eccentric shaft parts thereof. A radial piston type hydraulic motor consisting of a pressure oil supply oil passage and a pressure oil discharge oil passage each opening in a chamfered portion, and a radial piston type hydraulic motor driven by power taken out from a power take-off device of the vehicle, and supplying pressure oil to the radial piston type hydraulic motor. A hydraulic pump that supplies
A three-position, four-way switching valve is provided in a hydraulic circuit connecting the hydraulic pump and the hydraulic motor, and the hydraulic pump has a discharge capacity that is adjusted to a rotation speed of the hydraulic motor when hydraulically driven. The switching valve is set to match the rotational speed of the first gear of the rear wheels due to switching of the vehicle's transmission, and in its neutral switching position, the switching valve gently cuts off the oil supply path from the hydraulic pump to the hydraulic motor. At the same time, the hydraulic motor is electrically connected to the discharge oil path to the oil tank, and the hydraulic motor is brought into a freewheeling state by conducting the discharge oil path from the hydraulic motor to the oil tank. ing.

[Effect]

In a vehicle equipped with a hydraulic system configured as above,
By switching the 3-position 4-way switching valve, pressure oil is supplied to the radial piston type hydraulic motor from the hydraulic pump driven by the power extracted from the power take-off device connected to the gear transmission of the vehicle. When the casing supported on the fixed main shaft of the hydraulic motor is rotatably driven to hydraulically drive the front wheels, the rotational speed of the hydraulic motor during hydraulic drive changes to the first position of the rear wheels due to switching of the vehicle's transmission.
Since the discharge capacity of the hydraulic pump is set to match the rotational speed of the vehicle, hybrid four-wheel drive is performed in the first gear with hydraulically driven front wheels and normal mechanically driven rear wheels. . In addition, by switching the switching valve, the supply of pressure oil to the hydraulic motor is cut off, and the return oil from the hydraulic motor is released to the tank, thereby reducing the supply circuit pressure to below atmospheric pressure. , the hydraulic motor is in a freewheeling state, and the energy loss in the front wheels is minimal compared to the mechanically driven running of the rear wheels in 1st to 3rd speeds due to the transmission switching performed in this freewheeling state of the hydraulic motor. becomes.

〔Example〕

Hereinafter, preferred embodiments of this invention will be described in detail with reference to the drawings.

Fig. 1 is a side view showing a specific hydraulic motor used in the hydraulic system of this invention mounted on the front wheel hub, Fig. 2 is a hydraulic circuit diagram of this hydraulic system, and Fig. 3 is a hydraulic circuit diagram of this hydraulic system. Fig. 4 and Fig. 6 are hydraulic circuit diagrams of the device in which a standard configuration is used for the directional control valve and a bypass oil passage equipped with a check valve. FIG. 2 is a structural explanatory diagram of a specific casing rotation type radial piston type hydraulic motor used by being incorporated into a circuit.

In the figure, 1 is a radial piston type hydraulic motor with a rotating casing, 2 is a front wheel rim, 3 is a front tire, 4 is a fixed main shaft of the hydraulic motor 1, and 5 is a hydraulic pump. It is rotationally driven through a joint by the output shaft of a connected single-type power take-off device that rotates in one direction. 6 is an oil tank, 7 is a filter, 8 is a relief valve, 9, 9' is a manual operation type 3 position 4
It is a one-way switching valve. The directional control valve 9 has all ports in the neutral position, that is, the pump port P,
Tank port T, A connected to hydraulic motor 1,
The ball check valve 10 is incorporated into an all-port open, bypass-equipped directional control valve in which both B ports are connected to the oil tank 6. In the directional control valve 9', only the A port is blocked in the neutral position. and a ball check valve 10 is installed in the bypass line outside the valve, which replaces the directional valve 9 with a standard one having an A port block flow path in the neutral position, and A ball check valve 10 is attached to the conduit, and both of them have the same function as the directional switching valve 9.

The hydraulic motor 1 built into the left and right front wheels is
Each of the ports A and B of the switching valves 9 and 9' is connected in parallel via a conduit. 1
1 is a drain discharge pipe of the hydraulic motor 1;
In the figure, the frame surrounded by two-dot chain lines indicates that the hydraulic elements contained within this frame are compactly assembled into a compact hydraulic power source device that can be installed in a power take-off device (not shown). shows. The discharge capacity of the hydraulic pump 5 is
When it is rotationally driven by the power take-off device and the delivered pressure oil is supplied to each hydraulic motor 1 connected in parallel to the oil path by 1/2, the rotational speed of the casing of the hydraulic motor 1 is The first rear wheel by switching the transmission.
speed, that is, the low rotation speed.

Next, the operation of this vehicle running hydraulic system will be explained.

When the vehicle enters the rough terrain, the transmission is switched to 1st gear and the rear wheels are driven to rotate at low speed. At the same time, the directional control valve 9 or 9' is moved to the left position (forward position) by operating the manual switching lever. Switch to . Pressure oil from the hydraulic pump 5, which is rotatably driven by the output shaft of the power take-off device via a joint, passes through the oil passage inside the valve from the pump port P of the switching valve 9 or 9' to the port A, and then flows through the left pipe. 1/2 of each is sent to the hydraulic motor 1 through the passageway.
As described above, the discharge capacity of the hydraulic pump 5 is set to rotate the casing of each hydraulic motor 1 at a rotation speed that matches the rotation speed of the rear wheels. As a result, the rear tires are actively rotated at the same rotational speed as the rear tires, and the vehicle travels forward on rough terrain using four-wheel drive in first gear. In this case, the return oil from the hydraulic motor 1 passes through the oil path inside the valve from port B of the switching valve 9 or 9' to tank port T from the right pipe, and is discharged to the oil tank 6 via the right pipe. Along with being
Needless to say, the drain from the hydraulic motor 1 is discharged to the oil tank 6 via the drain discharge pipe 11.

When switching the switching valve 9 or 9' to the right position (reverse position) by operating the manual switching lever, the pressure oil from the hydraulic pump 5 is transferred to the pump port P.
From there, the oil passes through the oil path inside the valve to port B, and is sent to the hydraulic motor 1 through the right-hand pipe line in the same manner as described above, and drives the casing of the hydraulic motor 1 to rotate in the opposite direction. Therefore, by switching the transmission to the first gear/reverse position and operating the manual lever of the switching valve 9 or 9', the vehicle can be moved to the first gear position. The vehicle will be driven backwards.

Note that when the front wheels are rotated by hydraulic drive to drive, the rotational speed of both the left and right wheels must change automatically in order for the vehicle to turn smoothly. Since this causes a difference in the running resistance acting on the front wheels, the rotational speed of the hydraulic motor 1 that rotates both wheels separately changes automatically. By automatically increasing the amount of pressure oil flowing in and increasing the rotational speed compared to the side with greater rotational resistance, the same effect is achieved as if a differential gear were installed.

In addition, when switching the switching valve 9 or 9' to the left position (forward position) or right position (reverse position) by operating the manual switching lever and switching the transmission to the neutral position, the rear wheel The rotational drive by the engine is no longer performed, and the rear wheels are stopped or in a state of free rotation, but the output shaft of the power take-off device continues to be rotated by the engine, and the hydraulic pump 5 supplies pressure oil to the hydraulic motor 1. Since the fuel is continuously supplied, only the front wheels can be rotationally driven by hydraulic pressure, and the vehicle can be driven forward or backward by hydraulic drive alone.

When the switching valve 9 or 9' is switched to the neutral position by its manual switching lever, in the switching valve 9, pressure oil from the hydraulic pump 5 enters the valve from the pump port P, but the ball check valve 10 The oil passage is briefly cut off by the tank port T.
The supply of pressure oil from port A to hydraulic motor 1 is cut off, while the drained oil from hydraulic motor 1 is returned to oil tank 6 from port B via tank port T. It will be done. This also applies to the switching valve 9', and in the hydraulic circuit shown in FIG. However, since it is cut off by the ball check valve 10, the supply of pressure oil to the hydraulic motor 1 is cut off in the same way as described above, and on the other hand,
Drained oil from the hydraulic motor 1 is returned to the oil tank 6. Therefore, the front wheels are no longer rotationally driven by the hydraulic motor 1, but the vehicle's transmission is switched to, for example, the second or third speed (medium speed or high speed) position, and the rear wheels are driven. When the vehicle is traveling, the front wheels are naturally rotated at the same speed as the rear wheels, so the casing of the hydraulic motor 1 is rotated in the forward direction by the front wheels. When the casing of the hydraulic motor 1 is rotated in the forward direction while the supply of pressure oil to the supply oil path is cut off and the discharge oil path is open to the oil tank 6, , the pressure in the supply circuit is below atmospheric pressure, and the hydraulic motor 1 is placed in a freewheeling state, as will be described later, thereby minimizing energy loss. That is, when driving on a road or flat ground with rear wheel drive in second or third gear, by switching the switching valve 9 or 9' to the neutral position using the manual switching lever, The hydraulic motor 1 is placed in a freewheeling state, the rotational resistance of the front wheels is reduced, energy loss is minimized, and the vehicle can travel with almost the same fuel consumption as a conventional two-wheel drive vehicle. However, during this time, the hydraulic pump 5
Since oil continues to be sent to the circulating oil line from the pump port P of the switching valve 9 or 9' to the oil tank 6 via the tank port T, there is energy loss due to the line resistance, that is, the pump in the unloaded state. Although the power loss required for operation cannot be eliminated, the loss is small.

Switch the directional control valve 9 or 9' to the neutral position,
When the transmission is switched to first speed/reverse to move the vehicle backward, the hydraulic motor 1 is reversed via the front wheels as the vehicle moves backward, and acts as a pump. Therefore, since the left side pipe line of the hydraulic motor 1 becomes a discharge oil line, the ball check valve 10 is interposed in the oil line so that it can open freely and act as a relief valve.
prevents it from acting as a hydraulic brake.

Next, a casing rotating radial piston type hydraulic motor used in combination with these hydraulic circuits will be explained.

FIG. 4 is a front view of the radial piston type hydraulic motor with the bearing support cover removed;
FIG. 6 is a side sectional view thereof. In the figure, 15
1 is a casing, and 16 is a piston pressing surface, which forms a pentagonal surface on the inner periphery of the case 15. 17 is a piston, which is installed in each of five cylinders 19 provided radially at equal angular intervals toward the center _Oz of the cylinder block 18. Further, a piston ring is fitted near the bottom of the piston 17 to prevent oil leakage from between the piston 17 and the cylinder 19. Reference numeral 20 denotes an eccentric shaft portion of the fixed main shaft 4, and 21 and 21' denote a pair of left and right rolling bearings, which rotatably support the casing 15. Further, the eccentric shaft portion 20 is connected to the cylinder block 1.
8 is rotatably supported. The fixed main shaft 4 is provided with a supply oil passage 22 and a discharge circuit 23, both of which are opened at the two chamfered portions of the eccentric shaft portion 20.
It is connected to a port adapter 24 attached to the left end of the. Piston pressing surface 16 of piston 17
A pocket is provided at the top that makes contact with the piston 17, and a seal ring is fitted into the inner circumference of the pocket.
The pressure oil introduced through the hole penetrating the piston 17 is prevented from leaking from the contact area between the piston 17 and the piston pressing surface 16. 25 is a synchronizing pin embedded in the cylinder block 18, and 26 is a synchronizing ring fitted into the casing 15. The rotation of the cylinder block 18 relative to the casing 15 is regulated by the rotation synchronization mechanism composed of these two. ,
The top surface of the piston 17 and the piston pressing surface 16 are kept parallel to each other.

Next, the operation of this radial piston type motor will be explained.

By the pressure oil sent into the supply oil path 22, A
When the two pistons 17 at positions B and B are pressed against the piston pressing surface 16, the resultant force F of F ₁ and F ₂ is applied to the casing 1 via the piston pressing surface 16.
5. As shown in Figure 5, this resultant force F
is directed outward in a radial direction that crosses the center _O2 of the eccentric shaft portion 20 on which the cylinder block 18 is supported. On the other hand, the rotation center of the casing 15, which is rotatably supported via rolling bearings 21, 21' attached to the fixed main shaft 4, is _O1 . Therefore, the resultant force F has a torque arm corresponding to the sine of the resultant force F of the eccentricity _{1 2} , that is, _{1 3} with respect to the rotation center O ₁ of the casing 15, and the casing 16 has a torque arm of _{1 3} with respect to the resultant force F The torque causes it to rotate clockwise, as shown by the arrow, with _O1 as the center of rotation.

With this rotation, the piston 1 at E and D positions
7 is pushed inward by the piston pressing surface 16, the oil in the cylinder 19 is discharged as return oil from the discharge oil passage 23, and the cylinder 19 of the piston 17 at the C position is connected to the supply oil passage 22. In this case, at positions D and E, the piston pressing surface 16 receives a reaction force from the piston 17, and the resultant force generates a torque that rotates the casing 15 counterclockwise about the center _O1 , but its absolute value is as described above. The torque is small compared to the magnitude of the torque that turns the casing 15 clockwise. In the next step, the pistons 17 at the B and C positions close the A and B positions, respectively, and the casing 15 is turned clockwise as described above, causing the pistons 17 to close the E and D positions. The returning oil is discharged through the oil passage 23.
is discharged from. In the above description, the A position,
We have explained the generation of torque when the two pistons 17 that close the B position are subjected to the action of pressure oil, but since the four corners of the two-chamfered portion of the eccentric shaft portion 20 are cut out, When the piston 17 at position C moves slightly to position B, pressure oil acts on this piston 17 as well, so three pistons 17 may be affected by the pressure oil, and in this case, an even larger torque is generated. do. By continuously performing the above operations, clockwise torque is constantly applied to the casing 15, and rotation continues, so that the front wheel, which is integrally attached to the casing 15, moves forward. It will be rotated. Since the configuration of this hydraulic motor 1 is symmetrical, the supply oil passage 22 and the discharge oil passage 23
If it is reversed by the switching valves 9 and 9' of the hydraulic circuit,
It goes without saying that the casing 15, that is, the front wheels, is rotationally driven in the reverse direction opposite to that described above. A static pressure bearing is formed at the contact portion between the piston pressing surface 16 and the piston 17, and the pressing forces of the pressure oil acting on the top pocket and the bottom of the piston 17 are almost equal, so that the piston 1
The contact pressure of 7 against the piston pressing surface 16 is very small. Therefore, the friction loss due to the sliding movement between the top of the piston 17 and the piston pressing surface 16 that occurs as the casing 15 rotates becomes extremely small.

For convenience of explanation, it has been described above that the piston 17 is pressed against the piston pressing surface 16 by pressure oil, but in reality, a column of pressure oil approximately equal to the diameter of the piston directly presses against the piston pressing surface 16.
A rotation synchronization mechanism composed of a synchronization pin 25 and a synchronization ring 26 that prevents the cylinder block 18 from rotating beyond a certain rotation angle and keeps the top surface of the piston 17 and the piston pressing surface 16 parallel to each other. Since the cylinder 19 is provided with
The fit of the piston 17 against the piston 17 is
Since this fit gives the piston 17 a degree of freedom, the contact between the top end surface of the piston 17 and the piston pressing surface 16 is always maintained tightly. This, together with the action of the seal ring fitted into the top pocket of the piston 17, greatly reduces oil leakage from this contact.

Next, the supply of pressure oil to the supply oil path 22 is cut off by operating the switching valves 9 and 9' of the oil path circuit, while the return oil smoothly flows from the discharge oil path 23 to the oil tank 6. When the casing 15 is rotated clockwise by an external force (in this embodiment, the rotational force of the front wheels based on the forward running of the vehicle), the radial piston type hydraulic motor 1 becomes free. We will explain why the vehicle is in a wheeling state and can freely spin.

When the casing 15 is turned clockwise by an external force, the pistons 17 at positions E and D are pushed inward by the piston pressing surface 16, and the return oil is discharged from the discharge oil passage 23 to the switching valves 9, 9. ’ to oil tank 6
is discharged to. On the other hand, since the supply of pressure oil to the supply oil passage 29 is cut off by the switching valves 9 and 9', the pressure inside the cylinder 19 that acts on the inner end surface of the piston 17 that comes to the B and A positions again is depressurized.

Therefore, the force acting on the pistons 17 at positions B and A to push them outward and press them against the piston pressing surface 16 is weakened, and the casing 1
Separation of the piston 17 from the piston pressing surface 16 is facilitated by the differential pressure between the pressure slightly higher than the atmospheric pressure of the drain filling the space between the piston 5 and the cylinder block 18 and the pressure inside the cylinder 19. . When such an operation is repeated, negative pressure is generated in the cylinder 19, the piston 17 is drawn into the cylinder 19, and the cylinder block 1
None of the pistons 17 protrude from the outer periphery of the piston 8,
Therefore, no interference with the piston pressing surface 16 occurs, and the same effect as when the clutch is disengaged is obtained, and the casing 15 is freely rotated as a freewheel by the external force.

On the other hand, in preparation for switching the hydraulic motor 1 from a freewheeling state to normal operation, it is necessary that the relative position between the piston pressing surface 16 and the piston 17 in the circumferential direction be regulated within a certain range. be. The rotational synchronization mechanism consisting of the above-mentioned periodic pin 25 and synchronization ring 26 serves this purpose.

On the other hand, through this mechanism, the cylinder block 18
is rotated following the rotation of the casing 15, so when the casing 15 is rotated as a freewheel, as its rotational speed increases, the piston that is being drawn into the cylinder block 18 being rotated increases. When the centrifugal force acting on the piston 17 becomes larger than the suction force caused by the negative pressure that acts on the piston 17 and pulls it inward, the piston 17 moves toward the cylinder block 18.
It will become more prominent.

In this hydraulic motor 1, the casing 15
The rotational speed during third speed running in a freewheeling state is approximately 170 revolutions per minute, and a negative pressure that can sufficiently counteract the centrifugal force generated in the piston 17 due to this rotational speed must be maintained. I can do it.

Furthermore, when the hydraulic motor 1 is operated in a freewheeling state, the rolling bearings 21 and 21' that rotatably support the casing 15 and the cylinder block 18, respectively, and the bearing portion of the eccentric shaft portion 20 are lubricated as follows. The oil suctioned from the oil tank 6 through the drain discharge pipe 11 by the negative pressure in the casing 15 is sufficient to prevent problems such as seizure.

[Effect of idea]

Since this invention is constructed and operates as explained above, by using the vehicle running hydraulic system according to this invention to drive the front wheels, it is possible to move an agricultural truck, for example, to the first speed by switching the transmission. The vehicle can be driven with a hybrid four-wheel drive consisting of a mechanical drive for the rear wheels and a hydraulic drive for the front wheels, which improves driving performance on rough terrain and maneuverability compared to conventional systems that use only mechanical drive for the rear wheels. Its performance can be greatly improved in terms of wheel motion and hill climbing ability. In addition, when driving with the mechanical drive of the rear wheels as before, the hydraulic motor attached to the front wheels is placed in a freewheeling state by switching the directional control valve, minimizing energy loss. The vehicle can run with almost the same fuel consumption as a conventional two-wheel drive system, and the hydraulic motors on the front wheels do not perform any braking action when traveling backwards, so the vehicle can travel without any problems.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a specific hydraulic motor used in a hydraulic system according to the invention mounted on a front wheel hub, and FIGS. 2 and 3 are respectively
FIG. 4 is a hydraulic circuit diagram of this hydraulic system, and FIG. 4 is a front view of a specific casing-rotating radial piston hydraulic motor used in the hydraulic circuit, with the bearing support cover removed;
FIG. 5 is an explanatory diagram of the acting force of the hydraulic motor, and FIG.
The figure is a side sectional view of the hydraulic motor. 1...Radial piston type hydraulic motor with rotating casing, 2...Front wheel rim, 4...Fixed main shaft of hydraulic motor, 5...Hydraulic pump, 6...Oil tank, 9, 9'...Manual operation type 3-position 4-way switching valve, 10... Ball check valve, 15... Casing, 16... Piston pressing surface, 17... Piston, 18... Cylinder block, 19... Cylinder, 20... Eccentric shaft portion, 21 , 21'... Rolling bearing, 22... Supply oil path, 23... Discharge oil path.

Claims (1)

[Scope of utility model registration request] A cylinder block rotatably supported on an eccentric shaft of a fixed main shaft of a front wheel of a vehicle having an engine-driven rear wheel, and having a plurality of cylinders equally distributed radially toward the axis of the eccentric shaft. fitted into each of the cylinders of the block,
A piston having a through hole for introduction of pressure oil in the center and a pocket on the top end surface, a piston pressing surface inward that comes into close contact with the peripheral edge of the top end surface of each piston, and is rotatable about the fixed main shaft. A radial piston type hydraulic motor comprising a casing that is supported by a casing and forms a front wheel hub portion, and a supply oil passage and a discharge oil passage for pressurized oil that pass through the fixed main shaft and open at the two-chamfered portion of the eccentric shaft portion, respectively. , a hydraulic pump driven by power taken out from the power take-off device of the vehicle and supplying pressure oil to the radial piston type hydraulic motor; and 3 provided in a hydraulic circuit connecting this hydraulic pump and the hydraulic motor. and a four-way switching valve, the hydraulic pump having a discharge capacity such that the rotational speed of the hydraulic motor when hydraulically driven is equal to the rotational speed of the first speed of the rear wheels by switching the transmission of the vehicle. In addition, the switching valve, in its neutral switching position, cuts off the oil supply path from the hydraulic pump to the hydraulic motor, conducts it to the discharge oil path to the oil tank, and disconnects the oil from the hydraulic motor. 1. A hydraulic system for running a vehicle, characterized in that the hydraulic system is configured to bring the hydraulic motor into a freewheeling state by connecting a discharge oil path to a tank.